Quasielastic light scattering measurements of self-diffusion and mutual diffusion in gelatin solutions and gels
Quasielastic light scattering measurements of self-diffusion and mutual diffusion in gelatin solutions and gels
复制标题
明胶溶液和凝胶中自扩散和互扩散的准弹性光散射测量
DOI：
10.1007/bf00256498
复制
发表时间：
1981
期刊：
影响因子：
3.2
通讯作者：
Hyuk Yu
中科院分区：
文献类型：
--
作者：
E. Amis;P. Janmey;J. Ferry;Hyuk Yu
对于具有相同或几乎相同的化学结构和相同的聚合物浓度的交联凝胶，通过准弹性光散射测量的相互扩散系数的比较已经引起了相当大的兴趣。在一些情况下，相互扩散系数被发现是相同的(Jarry和Patterson 1982)或非常相似(Munch，et al.1977a、1977b)。在这里报道的研究中，对明胶的半稀溶液和由这些溶液在较低温度下形成的相应凝胶进行了准弹性光散射测量。尽管明胶由于其复杂的结构、不确定的凝胶化机制和广泛的分子量分布，在某种意义上是一种糟糕的聚合物选择，但它在凝胶温度以上表现为随机卷曲的聚合物(Veis 1964)，其凝胶的粘弹性对应于柔性链网络的粘弹性(Laurent，et al.1980)。在目前的研究中，粘弹性测量具有独特的优势(Laurent，et al.1980)之前已经提供了平移单体摩擦系数的值和宏观剪切模数G的精确值，因此可以检验散射和力学测量之间的关系。根据凝胶温度以上溶液的散射测量，确定了互扩散系数Dc和一个小得多的扩散系数D2，该扩散系数可被识别为聚合物的自扩散系数。对于凝胶，只得到Dc，并考察了它对温度和溶剂粘度的依赖关系(通过加入高达91%重量的甘油在很大范围内变化)。在所研究的范围内，先前观察到摩擦系数O和剪切模数G都取决于这两个变量(Laurent等人)。1980)。
There has been considerable interest in comparing the mutual diffusion coefficients, measured by quasielastic llghtscattering, for a concentrated or semidilute uncross-linked polymer solution and for a cross-linked gel having identical or nearly identical chemical structure and the same polymer concentration. In several cases, the mutual diffusion coefficients have been found to be the same (JARRY and PATTERSON 1982) or closely similar (MUNCH, et al. 1977a, 1977b). In the study reported here, quasielastic light scattering measurements have been made on semidilute solutions of gelatin and the corresponding gels that are formed from these solutions at lower temperatures. Although gelatin is in a sense a poor choice of polymer because of its complex structure, uncertain gelation mechanism, and broad molecular weight distribution, it behaves above the gel temperature as a random coil polymer (VEIS 1964) and the viscoelasticity of its gels corresponds to that of a network of flexible strands (LAURENT, et al. 1980). In the present study, it has the unique advantage that viscoelastic measurements (LAURENT, et al. 1980) of the same gels have previously provided values of the translatory monomeric friction coefficient ~oas well as accurate values of the macroscopic shear modulus G, so the relation between scattering and mechanical measurements can be examined. From the scattering measurements on solutions above the gel temperature, the mutual diffusion coefficient D c is determined as well as a much smaller diffusion coefficient D 2 which can be identified as the self-diffusion coefficient of the polymer. For the gels, only D c is obtained, and its dependence on temperature and solvent viscosity (varied over a wide range by incorporation of glycerol up to 91% by weight) is examined. Over the range studied, both the friction coefficient ~o and the shear modulus G were previously observed to depend on both these variables (LAURENT, et al. 1980).